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  • gen4-PA Power

    I would like to incorporate the gen4-PA board into a design. My question is how to allow both 5v power from USB, and battery on the 5v breakout line? Does this power pin have to be separated by a manual switch or is there a way to do this without manual switch isolation?

  • #2
    Hello geocentric,

    The gen4-PA was never specifically designed to be put into a final design, but I guess there are ways you could do it. You will need external components though.

    You could put a series diode onto the 5V pin of the gen4-PA, and have the battery feeding into this. If you then plug in the gen4-PA USB, the 5V coming in from USB will prevent the battery voltage passing if the battery voltage minus the diode drop is lower then a USB voltage. You will need to test this out. So when you use USB, the power will come from USB, and when you disconnect it will come from the battery. You will need to experiment with your voltages though and ensure you do get power from USB when USB is connected, and the battery is isolated. You basically want to prevent the voltages fighting, and the USB voltage pushing into the battery (ie charging it without management).

    Thats a simple and fairly crude way to do it, but given you can only access easily the voltage you would be putting into the 5V pin and not the USB voltage itself (unless you made a USB extension cable and access the voltages from on the cable... you could then compare the voltages with a comparitor circuit, and do a similar thing to the above, but a bit better.

    All comes down to how complex you want to go I guess. Might be easier to use a gen4-IB and a Programming Cable or uUSB-PA5, as you can then put a circuit in between them to handle battery vs programming voltages.

    Hope that helps

    Regards
    James

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    • #3
      Thanks for the thorough response! So, as I hear your options it sounds like a bad idea to try this ;-) I was hoping to avoid having to deal with soldering 30pin FPC connectors but this may be unavoidable.

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